Although the size of a puncture needle such as an injection needle used for human bodies is different depending on the application, the outer diameter is usually approximately 0.3 to 1.2 mm, and there is a puncture needle having a large outer diameter of 2 mm in some cases. A 31 gauge puncture needle generally used for insulin self-injection has an outer diameter of approximately 0.25 mm. The puncture needle having such a diameter gives piercing pain and wound when pierced, whereby patients who inject themselves with insulin particularly feel fear and anxiety. Thus, it is conventionally desirable to reduce the piercing pain from a puncture needle.
One way to reduce the piercing pain from a puncture needle is to reduce the outer diameter of the needle, and a 33 gauge ultrafine needle is already commercially available as a so-called painless insulin puncture needle with reduced pain. Meanwhile, there is a puncture needle in which a taper portion is provided at a needle tube barrel portion of the puncture needle, and a diameter of a needle tip portion is made smaller than a diameter of a base end portion connected to a syringe (see, Patent Literature 1).
Meanwhile, a needle tip of a puncture needle is usually required to have a certain size that allows a volume of infusion in a needle tube to be secured. Thus, there has been requited a method of reducing pain at the time of piercing without changing a usual diameter of a needle tip. One way to reduce piercing pain from the puncture needle is to reduce frictional resistance against a living body according to surface smoothing of a needle tube. For example, a rough surface having unevenness of 10 to several ten μm that is usually observed on a surface of a medical/sanitary tool is considered to cause pain at the time of injection into the living body in the case of the puncture needle, and there is proposed to polish the surface until the surface roughness becomes approximately 1 to 20 μm (see, Patent Literature 2).